System and method for adjusting the output of an output device to compensate for ambient illumination

• US 5,670,985 A
• Filed: 05/09/1994
• Issued: 09/23/1997
• Est. Priority Date: 05/09/1994
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Hernandez, Mathew, Cappels, Richard D. Sr.
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): KIM, JULIANA
• Application Number:
  US08/240,002
• Time in Patent Office: 1,233 Days
• Field of Search: 345/22, 345/153, 345/207, 348/184, 348/185, 348/189
• US Class Current: 345/601
• CPC Class Codes: G06F 3/04897 Special input arrangements or commands for improving display capability
• CPC Class Codes: G09G 5/02 characterised by the way in which colour is displayed details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607
• CPC Class Codes: H04N 5/58 in dependence upon ambient light

Abstract

A system for compensating the output of an output device to eliminate reflected ambient illumination comprises a display device, a calibration memory, a reflectivity memory, a memory, a processor, an input device, a video card, and an achromatic card that serves as a standard for comparison to the output of the output device. The reflectivity memory stores the reflectivity characteristics of the output device. The calibration memory stores the optical characteristics of the output device. The memory stores the reflectivity characteristics of the achromatic card, data, and program instruction steps of the system. The output of the output device is adjusted to match the ambient illumination reflected from the achromatic card. The processor then determines the tristimulus values of the ambient illumination through the known tristimulus values of the output generated by the output device, the reflectivity characteristics of the achromatic card, and the reflectivity characteristics of the output device. The processor then uses the tristimulus values of the ambient illumination to determine the bias setting of the output device to compensate all outputs generated by the output device for the ambient illumination reflected from the output device.

Claims

1. A system for compensating the output of an output device for reflected ambient illumination, the system comprising:

an output device having a controllable output and an input for receiving an output signal to be output on the output device;

a processor, having inputs and outputs, an output of the processor coupled to the output device; and

a memory, having inputs and outputs coupled to receive signals from and to send signals to the processor, the memory including routines for displaying a first set of discrete display regions on the output device, each display region in the first set having a different optical characteristic to provide a first range of optical characteristics for comparison to a reflection device with predetermined reflectivity characteristics, and routines for controlling the processor to adjust the output signal based upon a first selected display region chosen from the first set of discrete display regions to compensate for the effects of ambient illumination.

2. The system of claim 1, wherein the memory includes routines for displaying a second set of discrete display regions on the output device, the second set of discrete display regions including the first selected display region, the second set of discrete display regions providing a second range of optical characteristics for comparison to the reflection device, the second range of optical characteristics being narrower than the first range of optical characteristics.

3. The system of claim 2, wherein the optical characteristic is color.

4. The system of claim 2, wherein the optical characteristic is intensity.

5. The system of claim 1, wherein the memory comprises:

a calibration memory, having inputs and outputs coupled to the processor, for storing display characteristics of the output device; and

a reflectivity memory, having inputs and outputs coupled to the processor, for storing the reflectivity characteristics of the output device.

6. The system of claim 5, wherein the calibration memory and the refelctivity memory are read only memories.

7. The system of claim 5, wherein the memory further comprises:

a K₁ memory, having inputs and outputs coupled to the processor, for storing the reflectivity characteristics of the reflection device, the reflectivity characteristics of the reflection device including a first reflectivity constant; and

a program memory, having inputs and outputs coupled to the processor, for storing routines for controlling the processor for determining the ambient illumination and compensating the output of the output device for the ambient illumination reflectivity memory are read only memories.

8. The system of claim 7, wherein the routines for controlling the processor determines the ambient illumination using the reflectivity characteristics of the output device and the reflection device.

9. The system of claim 7, wherein the memory further comprises a pointer memory, having inputs and outputs coupled to the processor, for storing, in response to commands from the processor, an adjustment made to the output of the output device.

10. The system of claim 7, wherein the memory further comprises a compensated output memory, having inputs and outputs coupled to the processor, for storing, in response to commands from the processor, bias values for the output device compensated for ambient illumination reflected from the output device.

11. The system of claim 7, wherein the processor further comprises a current time generator.

12. The system of claim 11, wherein the compensated output memory also stores, with each set of compensated bias values, a record of the time at which such compensated bias values were generated by the processor.

13. The system of claim 12, wherein the program memory further comprises:

a time comparator for comparing the current time to data stored in the compensated output memory; and

an output adjuster, in communication with the time comparator, for automatically adjusting the output of the output device according to data stored in the compensated output memory.

14. The system of claim 1, wherein the output device is a computer monitor.

15. The system of claim 14, wherein the computer monitor is one from the group of:

a cathode ray tube, a liquid crystal display, and a gas discharge display.

16. The system of claim 1, wherein the output device is a printer.

17. The system of claim 1, wherein the output device is a photograph developer.

18. The system of claim 1, wherein the reflection device has uniform reflectivity for all wavelengths of visible light.

19. The system of claim 1, wherein the reflection device is an achromatic card.

20. A method for compensating the output of an output device for reflected ambient illumination, the method comprising the steps of:

providing a reflection device, having predetermined reflectivity characteristics, for comparing to the output of the output device;

adjusting the output of the output device to match the reflection device by selecting one of a plurality of output regions that matches the reflection device;

determining the tristimulus values of the output device at the adjusted level;

determining the ambient illumination reflected from the output device using the determined tristimulus values and reflectivity characteristics of the reflection device and the output device; and

calibrating the output device to remove the effect of the reflected ambient illumination from the output of the output device.

21. The method of claim 20, wherein the step of determining the ambient illumination comprises the steps of:

calculating tristimulus values of the ambient illumination reflected from the output device; and

generating a signal according to the calculated tristimulus values.

22. The method of claim 21, wherein the step of calibrating comprises the step of applying the signal to reduce the bias of the output device by the tristimulus value of the ambient illumination reflected by the output device.

23. The method of claim 21, wherein the signal generated in the generaling step is stored in a memory.

24. The method of claim 21, wherein the step of adjusting comprises the steps of:

displaying on the output device a first output region and a second output region that differs by a known amount in color; and

selecting one of the first or second output regions that most closely matches the reflection device.

25. The method of claim 21, wherein the step of adjusting comprises the steps of:

displaying on the output device a first output region and a second output region that differs by a known amount in intensity; and

selecting one of the first or second output regions that most closely matches the reflection device.

26. The method of claim 24, wherein the step of adjusting further comprises the steps of:

designating the selected output region as the first output region; and

repeating the steps of displaying and selecting.

27. The method of claim 24 wherein the first output region and the second output region are confined to outputs approximately described by the black body radiation of platinum.

28. A system for adjusting color and intensity to compensate for ambient illumination, the system comprising:

an output device having a controllable output and an input for receiving an output signal to be output on the output device, the output device having predetermined reflectivity characteristics;

a first means, having inputs and outputs coupled to the output device, for calibrating the output device to a reference output;

a first adjustment means, having inputs and outputs coupled to the first means and the output device, for generating a signal to adjust the output of the output device;

a determining means, having inputs and outputs coupled to the first means, for determining the tristimulus values of the output device at the adjusted level;

a calculating means, having inputs and outputs coupled to the first means, the first adjustment means, and the output device, for calculating the ambient illumination reflected from the output device using the determined tristimulus values of the output device, the reflectivity characteristics of the output device, and the reflectivity characteristics of the reference output; and

a second adjustment means, having inputs and outputs coupled to the first means, the first adjustment means, the calculating means, and the output device, for generating a signal to adjust the output of the output device by the amount, calculated by the calculating means, of ambient illumination reflected from the output device.

29. A method for compensating the output of an output device for reflected ambient illumination, the method comprising:

providing a reflection device, having predetermined reflectivity characteristics, for comparing to the output of the output device;

displaying a first set of discrete display regions on the output device, each display region in the first set having a different optical characteristic to provide a first range of optical characteristics;

comparing the optical characteristics of the first set of discrete display regions to the reflection device;

selecting a first selected display region from the first set of discrete display regions; and

adjusting the output of the output device based upon the first selected display region to compensate for the effects of ambient illumination.

30. The method of claim 29, further comprising:

displaying a second set of discrete display regions on the output device, the second set of discrete display regions including the first selected display region, the second set of discrete display regions providing a second range of display characteristics for comparison to the reflection device, the second range of optical characteristics being narrower than the first range of display characteristics;

selecting a second selected display region from the second set of discrete display regions; and

adjusting the output of the output device based upon the second selected display region to compensate for the effects of ambient illumination.

31. The method of claim 30, wherein the optical characteristic is color.

32. The method of claim 30, wherein the optical characteristic is intensity.